The long and short of it:
SASUKE is another victim in a series of cuts by TBS that includes other longtime shows such as Tokyo Friend Park and Kinpachi Sensei. (I thought TBS was canceling Mito Komon too but I guess not). Plus, the annual K-1 New Year's Eve event Dynamite!! is probably over as well. TBS, which has been lagging behind the other networks for years, is probably realizing something along the lines of what this blogger said last year.
I wish I could find it but someone on a 2ch thread said pretty much everything being said in the article above back in early January: That they had sold off the Sportsman No. 1 set (to who?) and that the last SASUKE show would be in March of this year. Since that was all spot on, I'd like to add that the person also stated that the last show would be a retrospective so we may have already seen the last SASUKE competition and not even known.